Room dir: New filtering & 3rd party networks

Changes filtering on 3rd party networks to divide into portal / non portal rooms and not show portal rooms by default. Adds a special '_matrix' network for all rooms that aren't portal rooms.

Also adds ability to query 3rd party directory servers.

src/skins/vector/css/vector-web/views/directory/NetworkDropdown.css

@@ -52,6 +52,10 @@ limitations under the License.
     vertical-align: middle;
 }
 
+input.mx_NetworkDropdown_networkoption, input.mx_NetworkDropdown_networkoption:focus {
+    border: 0;
+}
+
 .mx_NetworkDropdown_menu {
     position: absolute;
     left: -1px;